C3 Corvette Engine Swap - The Construction Zone

Some Unexpected But Solvable Complications Arise As The C5 Shark Gets Its LS1 Fitted In Place

All sorts of cliched comments come to mind when I think about my C5 Shark project. In some respects it's like a bad news-good news joke, or I could do a poor paraphrasing of the old Star Trek "going boldly where no one has gone before" line. Maybe "if I'd only known then what I know now" would be apropos. Regardless, I made a commitment to this concept-an LS1 and 4L60E installed in a third-gen Corvette-nearly two years ago, and sealed the fates of both myself and what I originally nicknamed the (not so) Great White when the '76 Stingray's L48 small-block and Turbo 350 went to a new home in a needy '68 Camaro.

As I've outlined before, ain't nuthin except being a General Motors V-8 engine and bore spacing that's common between the venerable and beloved Chevy small-block and GM's Gen III that, in various configurations, is found in Corvettes, Camaros, Firebirds, and pickup trucks. Boy, does that ever make things interesting!

Last month I mentioned that Bow Tie Overdrives, a Southern California company that specializes in 700-R4 swap kits for older Chevy (and other GM) products, was handling not only the details of installing a 4L60E in the old Shark but had also volunteered to take a stab at making the LS1 fit.

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While the final transmission crossmember will be very similar to what we showed in last month's installment, the motor mount setup of just a few weeks ago turns out to have been the first of several concepts that the boys at B.T.O. tried and tossed before coming up with what we'll show right now as templates for the "stands" that are being fabricated as this is written. Using an adapter plate with traditional 350 small-block side mounts and custom frame stands-as shown last month-are completely out of the picture. The final setup utilizes F-body LS1 mounts in the factory location, bolting directly to new, custom stands that will be welded to the frame. The custom LS1 stands also straddle both the steering box (on the driver's side) and the idler arm (on the passenger side), and are designed to allow full access to the steering components and the hardware that affixes those components to the frame.

The centerline of the LS1's crankshaft and the driveline are essentially identical to the factory's alignment of the original 350/TH350. With the GM Performance Parts LS1 and 4L60E (PNs 25534322 and 12497318) mocked up in what will be within hundredths of an inch of their final locations, B.T.O. has confirmed that the stock '76 power steering ram barely clears the oil pan; that the F-body LS1 exhaust manifolds fit very well within the old Corvette's frame, steering box, and column; and we know for certain that the accessories (power steering pump, air conditioning compressor, and alternator) will not fit in either C5 or F-body configurations.

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One of Bow Tie Overdrives' technicians holds a template for final version of the driver's side motor mount stand. The faint lines on the side of the template near Jason's right hand indicate where the windows will be.

So, the engine and transmission mounts are pretty much finalized. Next month we should be able to show both the finished trans crossmember and the motor mount stands welded in place in the C5 Shark's frame. We've removed the original gas tank and shipped it off to Rock Valley Antique Auto Parts, a company well known and highly regarded in the street rod hobby for their stainless steel gas tanks, to be replicated in stainless and completely set up (wiring, fittings, in-tank-and correct-electric fuel pump with filter, baffling, etc.) to fit in the '76 and work with the LS1. Once we have the new gas tank we'll start fabricating the new fuel lines.

Meanwhile, the Shark's original radiator is in position and, once a couple of cooling system fitment problems are resolved, will become a mock-up for where hoses and lines need to be located on a new and, naturally, custom radiator to fit the '76 Corvette's core support and work properly with the LS1.

We'll be back next month with another update on the progress of the C5 Shark. With any luck at all, we can show the old and new fuel tanks, the mock-up for the radiator, and a trick, workable, and custom solution to the accessory mounting problem. The LS1 engine swap has proven to be much more complex than we'd expected. But what has been and is still being learned will ultimately be seen as a kit (or series of kits and components) that'll make it possible for owners of '63 through '82 Corvettes to install the incredible LS1 in their cars without going to a drastically modified frame and suspension (i.e. Car Creations' C4 suspension conversions), and without starting from scratch like we've done. See ya on the next lap.

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C3 Corvette Engine Swap - The Construction Zone

One of Bow Tie Overdrives' technicians holds a template for final version of the driver's side motor mount stand. The faint lines on the side of the template near Jason's right hand indicate where the windows will be.

Here are above and from below looks at the basic configuration of the driver's side LS1/Shark motor mount stands. The final parts will be contoured very cleanly around the steering box and will have "windows" that'll both look cool and allow (relatively) easy access to the steering box and its mounting bolts. First and foremost, the C5 Shark has to be completely functional, serviceable, and drivable.

Two perspectives from "down under" show how the passenger side LS1 mount will straddle the idler arm.

The finalized version will give reasonably good access to the idler arm mounting nuts and bolts.

This simple aligning jig was created with a stock 350 block and the GMPP 4L60E computer-controlled automatic overdrive transmission in position to ensure that the LS1's crankshaft centerline would end up in the same alignment as was originally engineered by GM. Note how much extra room there is in front of the LS1-it's a lot shorter (front to back) than the original small-block.

We weren't kidding about extremely tight tolerances. There's about 1/4-inch clearance between the oil pan and the power steering ram. Clearance would be nonexistent with a C5-spec or and truck-spec oil pan.

Here's a look at a close-to-final configuration 4L60E/Shark trans crossmember. The final crossmember will bolt to the original locations on the frame and will have bracketry for the parking brake cable assembly. Note how the tubular K-member follows the contours of the floor. This will greatly simplify fitting a custom, efficient, and emissions-legal (we gotta run "cats" just like a late LS1 Camaro or Firebird, or a C5) exhaust.

Speaking of tight or nonexistent clearances, check out the fit between the passenger side of the LS1 water and the right upper control arm.

The two holes on the side of the pump are where fitting were for the heater hoses. These will be plugged and new holes-and fittings-will be situated on the bottom of the housing where there's plenty of room.

We take a 5.3L LS1 engine and throw in a few performance upgrades and test it with a carburetor and EFI computer tuned to see what horsepower we get. Only at www.superchevy.com, the official website for Super Chevy Magazine. » Read More

In this month's quest to find a 1987 Chevy Corvette C4 that addresses both these issues, we tracked down one Corvette owner who was able to swap out his car's long-in-the-tooth L98 for a cammed-up LS1 engine. Even better, he did the entire project for less than $5,000. - Vette Magazine » Read More